For network client applications, such as web browsers, a limiting performance factor is often low bandwidth to the server. To mitigate this low-bandwidth problem, network client applications often cache content replicated from servers, so that as much information as possible is kept available on the client user's hard drive. To cache content, the local machine generates a filename from the content's URL (Uniform Resource Locator) and stores the file in the application's cache directory (folder). As data access times from the hard drive are typically orders of magnitude faster than download times, some or all of a server's content may often be rapidly accessed from the cache with little or no downloading of data from the server. In the extreme case, the computer or server may be offline from the network, in which case the cache may still provide some version of the content.
While content caching thus provides substantial performance improvements, one problem is the time taken for the downloading of the content into the cache. Because this downloading operation can be extremely slow, particularly with large amounts of data, content providers are seeking alternative delivery vehicles, such as CD-ROMs, for pre-filling browser caches, especially for static content. One known approach to pre-filling caches with content is to copy the content from a CD-ROM or the like into the web cache of an application, such that when seeking to retrieve the content, the application will find the desired content in the cache as if it was previously downloaded and cached. However, this is a relatively slow and space-consuming process, given the capacity of CD-ROMs versus a typical hard drive. For example, CD-ROMs may contain approximately 650 megabytes of data, which may be distributed among thousands of files, and thus it may take a long time to copy such a large amount of data into the cache. Moreover, if the browser cache enforces a size quota, the pre-filling operation may overflow the cache and/or displace existing content. In turn, the pre-filled cache files may be displaced by other content that is subsequently downloaded or pre-filled. Thus, this approach has a number of drawbacks associated therewith.
Another approach is to author web pages using "file: references" to hard drives or CD-ROMS. When the page is accessed, the application retrieves the content from the appropriate media location, as determined by the file system reference, rather than from the web site. However this approach is restrictive because drive letters of personal computers may be configured many different ways. If the drive letter or letters chosen by the web site do not correspond to the right type of drive, or not enough space is available, then errors will likely occur and the user will see error messages.